If SHA256 is successfully attacked, what measures will be taken to replace the compromised hash function?
In the event of a SHA256 attack, will it be necessary to re-timestamp the entire blockchain from the beginning?
What are the potential challenges and implications of switching to a new hash function in the blockchain?
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2This question is similar to: If SHA256 and/or RIPEMD-160 were broken, would all bitcoin addresses be compromised?. If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem.– RedGrittyBrickCommented Jun 29 at 14:53
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1 Answer
There was a similar question to this on the BitcoinTalk forum in 2010, to which Satoshi Nakamoto contributed:
SHA-256 is very strong. It's not like the incremental step from MD5 to SHA1. It can last several decades unless there's some massive breakthrough attack.
If SHA-256 became completely broken, I think we could come to some agreement about what the honest block chain was before the trouble started, lock that in and continue from there with a new hash function.
If the hash breakdown came gradually, we could transition to a new hash in an orderly way. The software would be programmed to start using a new hash after a certain block number. Everyone would have to upgrade by that time. The software could save the new hash of all the old blocks to make sure a different block with the same old hash can't be used.
